Investigation of the excavation disturbed zone due to the excavation of horizontal galleries; Study in the Horonobe Underground Research Laboratory

Kubota, Kenji*; Aoyagi, Kazuhei  ; Sugita, Yutaka 

In an excavation of shafts and galleries in the deep underground for disposing high level radioactive waste, an excavation disturbed zone (EdZ) or excavation damaged zone (EDZ) is developed around the shafts and galleries owing to the stress redistribution. It is important to understand the behavior of the EdZ or EDZ because these zone could have an effect on the transfer behavior of radioactive nuclide. Therefore, the authors performed the in situ experiment to investigate the behavior of EdZ or EDZ in the 140m and 250m gallery in the Horonobe Underground Research Laboratory. From the result of the experiments, the authors compared the characteristics of EdZ or EDZ between those in 140m and 250m gallery. The extent of the fractures induced by the gallery excavation, i.e., EDZ was about 0.45m in the 140m gallery and about 1m in the 250m gallery. The extent of the unsaturated zones related with EdZ was about 1m in the 140m gallery, however, unsaturated zone was not appeared in the 250m gallery.